Some micromachined (“MEMS”) accelerometers detect acceleration by sensing the displacement of a proof mass, or beam. Some accelerometers quantify the displacement of a beam by assessing the change of resistance in a piezo element coupled to the proof mass. Other accelerometers quantify the displacement by assessing a change of capacitance caused by the displacement of the beam, for example if a portion of the beam forms a variable capacitor with a substrate, or with sensing fingers.
Some capacitive accelerometers quantify the displacement of a beam by comparing a capacitance formed by the beam with a reference capacitance. For example, some prior art capacitive accelerometers include a reference capacitor that is separate from the beam, and that is ideally a fixed capacitance.